高斯型耦合Tavis-Cummings模型中原子的熵压缩

利用全量子理论研究了高斯型耦合Tavis-Cummings模型中一个原子的熵压缩,运用数值计算方法讨论了原子垂直于腔轴的运动速度、光场强度以及两原子的初态对单个原子熵压缩的影响. 结果表明,原子的熵压缩时间由原子的运动速度决定,压缩程度由光场强度决定,压缩时间和压缩程度还决定于原子的初始状态.     

纠缠双原子对场熵压缩特性的影响

研究了相干态光场与纠缠双原子相互作用系统中场熵的压缩性质,借助于数值计算,讨论了双原子纠缠度及光场强度对场熵压缩的影响。所得结果表明,双原子初态的纠缠度对压缩的持续时间和压缩深度具有决定性的影响。当双原子初始时刻处于最大纠缠态时,场熵具有较大的压缩深度和较长的压缩时间。初始光场强度对场熵的压缩深度和压缩时间也具有显著的影响。光场愈弱,场熵的压缩性愈好。     

Ξ型三能级原子玻色-爱因斯坦凝聚体对光场压缩性质的影响

利用格子液体方法对Ξ型三能级原子玻色-爱因斯坦凝聚体与单模压缩相干态光场相互作用系统的哈密顿量进行了改进, 并且研究了Ξ 型三能级原子单模光场系统中光场压缩性质.结果表明: 光场两正交分量交替呈现周期性压缩, 其最大压缩深度由光场与原子间的相互作用强度和光场初始压缩因子决定, 而压缩时间与光场的圆频率有关. 关键词： 玻色-爱因斯坦凝聚 Ξ型三能级原子 压缩相干态 单模压缩态光场     

运动原子与光场依赖强度纠缠下最佳熵压缩态的制备和控制

运用量子信息熵理论,研究了运动二能级原子与光场依赖强度纠缠下最佳熵压缩态的制备和控制;比较了分别从基于信息熵不确定关系和海森堡不确定关系出发得出的结果;分析了制备原子最佳熵压缩态的充要条件,并进行了数值验证.考察了场模结构参数对最佳熵压缩态的影响.结果表明,信息熵压缩是对原子压缩效应的高灵敏量度;控制原子与场的相互作用时间,斩断原子和场的纠缠,选择原子的相干性,调节系统的相对位相可制备原子最佳熵压缩态;控制场模结构参数,可获得持续的原子最佳熵压缩态. 关键词： 依赖强度耦合 场模结构参数 最佳熵压缩态     

单模辐射场与耦合双原子相互作用系统中场熵的压缩特性

研究了单模辐射场与耦合双原子相互作用系统中场熵的压缩特性,讨论了系统初始状态及原子间偶极相互作用对场熵压缩特性的影响.数值计算结果表明,当系统初始时刻处于合适的相干叠加态时,场熵呈现出周期性压缩现象,其压缩深度和压缩时间与原子间偶极相互作用强度有关. 关键词： 单模辐射场 耦合双原子 光场熵压缩     

强度关联耦合下两个二能级原子与Pólya态光场相互作用系统的量子特性

利用全量子理论计算方法,探究了在强度关联耦合下两个二能级原子与单模Pólya态光场相互作用系统中原子线性熵粒子布局数反转以及信息熵压缩随时间的演化规律.分析了原子初态、光场参量p和r以及Lamb-Dicke参量η对原子线性熵、粒子布局数反转以及信息熵压缩的影响.结果表明:当原子处于不同的初态时,相互作用系统表现出完全不同的量子特性;光场参量p增大使得各个物理量振荡周期增大;光场参量r增大,使振幅发生变化,破坏粒子布局数反转崩塌-复原现象以及信息熵压缩效应.     

k光子Jaynes-Cummings模型光场的熵压缩

研究了k光子Jaynes-Cummings模型光场的熵压缩,讨论了光子数k和原子的初始状态对光场熵压缩的影响.结果表明,随光子数k的增大,光场的位置熵压缩愈趋明显,动量熵压缩量减小;当k≥3时,位置熵始终是被压缩的.原子的初态对光场的熵压缩也有一定的影响.     

二能级原子玻色-爱因斯坦凝聚体与双模光场相互作用系统中原子激光的压缩性质

利用格子液体方法对二能级原子玻色-爱因斯坦凝聚体与双模光场相互作用系统的哈密顿量进行了改进,并且研究了系统中原子激光的压缩性质.结果表明:原子激光的两个正交分量均可被周期性压缩,其最大压缩深度主要依赖于光场初始压缩因子,而崩塌-回复振荡频率和量子Rabi振荡频率主要分别由光场与原子间的相互作用强度和光场圆频率决定.     

Bell态原子与双模纠缠相干光场双光子相互作用系统的量子纠缠

运用全量子理论和数值计算的方法,借助于原子的量子约化熵研究了初始处于Bell态|β00>和| β10>的两原子与双模纠缠相干光场双光子相互作用系统中两原子与双模光场之间纠缠的演化特性.分析了光场强度、光场纠缠度及原子间相互作用强度对原子熵演化特性的影响.结果表明:随着双模光场的平均光子数的增大,原子熵的时间演化曲线逐渐变为规则振荡;增大原子间的相互作用强度,原子熵的振荡频率和振幅都减小;改变双模光场的纠缠度,原子熵的振荡频率和振幅都不发生改变.     

Ξ型三能级原子玻色-爱因斯坦凝聚体单模光场系统中双模原子激光的压缩性质

研究了Ξ型三能级原子玻色-爱因斯坦凝聚体单模光场系统中双模原子激光的压缩性质.结果表明:双模原子激光能被周期性压缩,并且具有量子Rabi振荡和崩塌-回复现象两种形式的振荡.最大压缩深度和崩塌-回复振荡频率主要依赖于光场与原子间相互作用强度,量子Rabi振荡频率主要由光场圆频率决定.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.